The lower Paleozoic Sicamous Formation (Mount Ida Group) comprised of calcareous phyllite and limestone is underlain by schist of the Hadrynian and/or Paleozoic Silver Creek Formation (Mount Ida Group). This sequence is intruded by altered Cretaceous? granites and capped by Eocene volcanics of the Kamloops Group.
The Miller tunnel, about 83 metres long, is in strongly fractured and silicified, micaceous metasediments less than 20 metres north of a granitic intrusion. The tunnel follows a northeasterly trending shear containing a quartz vein system mineralized with sphalerite, galena, chalcopyrite and pyrite. In 1918, a 1.4-metre sample across the full width of the face (at the bottom) analysed 8.2 grams per tonne gold and 0.68 gram per tonne platinum. Another sample from a mineralized streak, 3.8 centimetres wide, in the face, analysed 4.7 grams per tonne gold and 1.02 grams per tonne platinum (Munition Resources Commission, Final Report 1920, page 185). Recent work has failed to duplicate the gold and platinum values.
Trenches expose strongly altered and fractured micaceous and locally calcareous metasedimentary rocks. Original textures are obscured by strong silicification or phyllic alteration (quartz-clay-sericite-pyrite). A number of milky quartz veins trending east to northeast cut both types of alteration. They locally reach 20 centimetres in width, though generally are much narrower and in swarms with blebs of pyrite, galena, sphalerite and some finer chalcopyrite. A 2.0-metre true width sample across a quartz vein zone in phyllic alteration yielded 13.65 per cent lead, 0.18 per cent copper, 0.35 per cent zinc, 0.58 per cent tin and 0.17 per cent antimony (Assessment Report 19867, page 11).